002E84

What the Code Means

Code 002E84 (and its companion 002E85) is stored in the engine control module (DME) when communication with the electric coolant pump is lost. The pump is controlled over the BSD (Bit-Serial Data Interface) bus, and the fault points to a data exchange failure between the DME and the pump electronics.

A common cause of unstable pump electronics is a drop in capacitance of the electrolytic capacitor mounted inside the pump behind the aluminum cover. The factory part is a Nichicon BX 220uF, 35V, 150°C capacitor, 12.5 mm in diameter and 25 mm long. When this capacitor degrades, the supply voltage to the pump electronics becomes unstable and BSD bus communication drops out.

A cooling system with an electric pump needs constant data exchange to regulate output. When communication fails, the DME may enter limp mode and limit engine load.

Symptoms

• 002E84 or 002E85 “Electrical cooling pump, communication” stored in DME memory.
• Possible engine power limitation or limp mode while the fault is active.
• Unstable cooling system operation, possible overheating during extended driving with the fault present.

Diagnosis and Repair

Capacitor Check

1. Remove the electric coolant pump.
2. Open the aluminum cover on the back of the pump to access the capacitor.
3. Measure the capacitance. Nominal value: 220 µF ± 20% at 120 Hz and 20°C.
4. If the measured capacitance is well below spec, replace the capacitor with a new one rated: Nichicon BX 220uF, 35V, 150°C, D = 12.5 mm, L = 25 mm.

BSD Bus Check

For faults related to BSD bus communication loss, check the signal with an oscilloscope:

• Frequency: 100+ kHz
• Sample rate: 50–100+ kS/s
• Amplitude: 12Vpp

Make sure there are no opens, shorts, or interference on the BSD line between the DME and the pump.

Secondary Problems

Ignoring a communication fault with the electric coolant pump can lead to the following:

• Disrupted coolant circulation and engine overheating.
• Excess oil (with related faults) raises internal engine pressure and vacuum, which can cause gasket leaks.
• Oil entering the intake through the turbocharger and, in some cases, a clogged engine breather.